1. Field of the Invention
The present invention relates to an inkjet head which ejects ink to a recording medium to perform printing thereon, and a method for manufacturing the inkjet head.
2. Description of the Related Art
In an inkjet head which is used in an inkjet printer or the like, ink supplied from an ink tank is distributed to a plurality of pressure chambers. A pulsed pressure wave is selectively applied to the pressure chambers to eject ink from nozzles. As a means of selectively applying pressure to the pressure chambers, an actuator unit may be used. In the actuator unit, a plurality of piezoelectric sheets made from piezoelectric ceramic are laminated.
As an example of such an inkjet head, there is known an inkjet head having an actuator unit in which a plurality of continuous flat-plate-like piezoelectric sheets extending over a plurality of pressure chambers are laminated, and at least one of the piezoelectric sheets is put between a common electrode shared by a large number of pressure chambers and kept in ground potential and a large number of individual electrodes, that is, drive electrodes located in positions opposed to the pressure chambers respectively (see JP-A-4-341852 (FIG. 1)). Each part of the piezoelectric sheet put between the individual electrodes and the common electrode and polarized in the laminated direction expands and contracts in the laminated direction by so-called piezoelectric longitudinal effect due to an external electric field applied to the piezoelectric sheet in the polarizing direction thereof when the individual electrodes on the both sides of the part put between the individual electrodes and the common electrode are brought into potential different from that of the common electrode. In this event, the piezoelectric sheet part put between each individual electrode and the common electrode serves as an active layer which can be deformed due to piezoelectric effect when an external electric field is applied thereto. As a result, the volume of a pressure chamber corresponding to the part is changed so that ink can be ejected toward a recording medium from a nozzle communicating with the pressure chamber.